Protective coating



June' 7 c. H. FRANKs PROTECTIVE COATING Filed ADE. 26. 1925 PatentedJune 28, 1927.

UNITED STATES i, 1,633,576 PATENT OFFICE.

OLEI H. FRANXB, l' LA GRANGE, ILLINOIS, ABBIGNOB T0 WESTERN ELECTRICCOM- PANY, INCORPORATED, OF YORK, N. Y., A. CORPORATION 0F NEW YORK.

rmac'rrvn courre.

Appunti mea aan se, .1925. semi no. 52,697.

This invention relates to a protective coating and a method of producingsuch a coating. Y

The .principal object of this invention is to produce an improvedprotective coating which is tough but relativel flexible, in anefficient, reliable and expeditious manner.

In order to obtainy this object in accordance with one embodiment of theinvention, a cellulose derivative in fiber or strand form, arranged inany manner, may be subjected to a solvent to dissolve portions thereof,thereby causing the .adjacent fibers or strands to coalesce thus formingan imperforate film or coating reinforced by theundissolved portions ofthe fibers or strands. The strands may also be composed of naturalfibers and impregnated with a cellulose derivative and arranged inunwoven warp formation before subjection to the solvent for thecellulose derivative. In order to prevent undue shrinkage upon theevaporation of the solvent, the fibers or strands may be impregnatedwith an agent which retards or prevents the hardening of the cellulosederlvative. A coating formed in either manner may be employed toadvantage in making protective and insulating covers or envelopes forelectrical coils.

These and other features of the inventlon will be clearly comprehendedfrom the following description taken in connection with the accompanyingdrawings, in which- Fig. 1 is a view in elevation of an electrical coilhaving a coating embodying the invention and prgduced according to theimproved method,"part of the coil being broken away to more clearlyillustrate the details of the structure; e

Fig. 2 is a vertical section taken on the line 2-2 of Fig. 1 looking inthe direction of the arrows;

Fig. 3 is an enlarged fragmentary view in elevation of the coil shown inFig. 1, illustratin schematically one of the steps of the metho;

Fig. 4 is a plan view of a plurality of interwoven strands before andafter treatment with the solvent to produce a coating; and

Fig. 5 is a vertical section taken on the line 5-5 of Fig. 4 looking inthe4 direction of the arrows.

When practicing the invention it is apparent that the process dividesitself quite naturally into two main divisions: first, the

preparation and arrangement of the fibers or strands, and secondly, thetreatment therey of to form an imperforate sheet. In order to slmplllfythe description these two divisions of t e process, each including aplurality ofl steps, will now be described in the order in which theywere enumerated.

The ty e of fiber or strand em loyed may be any fi er or strand of acellulose nature, such as the cellulose derivatives, which in a mannerto be described later, may be treated with a solvent to produce theeffect desired. Examples of such materials are the strands of artificialsilk which are made up of a plurality of synthetic filaments or ends.These strands may be employed for practicing the invention without anyadditional treatment. Strands of natural vegetable or animal fibers,suchas cotton or silk threads, may be employed but they must beimpregnated with a cellulose derivative, such as nitro-cellulose or`cellulose acetate, before they are in con-A dition for use.

When the type of strand to be used has been selected lengths thereof maybe arranged in an unwoven manner, such as solely 1n an unwoven warpformation, inthe form of a web or in whatever other form is de-` siredand which will permit the successful. treatment by the second divisionof the process. When employed to form a waterproof and insulatin coverfor an electrical conductive winding 10 of an electrical coil Figs. 1, 2and 3), designated generally by t e numeral 11 having a core 20 and endpieces or spool heads 21, the strand is preferably arranged in a seriesof adjacent helices 12. As an alternative a plurality of strands may beinterwoven as indicated in that portion of Figs. 4 and 5 indicated bythe numeral 13.

The fibers or strand having been selected and arranged in a suitablemanner as indi cated in the preceding paragraph, the next division ofthe process may be performed. This includes the subjection of theassembled fibers or lengths of strand to a solvent for the cellulosederivative, to produce an imperforate sheet. The solvent may be appliedin a number of Ways depending upon the specific arrangement of thefibers or strands and the results desired. As an example, they may besprayed with a solvent or sub- 'ected to the vapor of a solvent durinthe boiling thereof. When the associated bers 110 or strands aresubjected to the solvent, particularly in vapor form, they becomepartiall dissolvedor fused in a manner which mig t be termed autogenousagglutination. The closely associated ,individual fibers or strands thuscoalesce or adhere to each other, and after beinndried to evaporate allof the solvent, the 'shed imperforate coating resents the appearance asshown at l5 in ig. 3 or at 16 1n Figs. 4 and 5. The coating whencompleted is homogeneous and shin on one surface where the solventaction has en applied to the strands, but on the opposite portion of thecovering the strands will still be found to retain their originalindividual character.

The solvent employed may be any of the well known solvents for thecellulose derivatives. Acetone, however, is preferred because thismaterial is a good solvent for both cellulose acetate and cellulosenitrate and is easily handled. Other solvents, however, which may beemployed are a mixture of ether and alcohol, tetrachloralethane,ethylacetate, diacetone alcohol, methyl'ethyleketon or benzol acetate.ln addition to true solvents, partial solvents or so-called plasticisersmay be employed, such as furfural.

ln the protection and insulation of electrical coils, other cellulosematerial may also be employed with the waterproof Coating describedabove, to form a protective coating or envelope entirely surrounding theturns of the coil. In providin this form of coatin a core portion of celulose material 25 @gigs l and 2) may be formed around the core 20, andend pieces 26 of the same material formed adjacent to the spool heads21, and made integral with the core portion 25. The turns or windings 10of the electrical coil may then be applied around the core ortion 25 andbetween the end pieces 26. hereafter the windings may be covered withhelices l2 of cellulose material in strand form (Fig. 3), the entirecoil subjected to the action of a 'solvent preferably in vapor form. Thestrand covering is thus formed into an imperforate sheet, as describedhereinbefore, and imperforately connected, cemented or coalesced withthe end pieces 26, thus producing a continuous imperforate waterproofcoating, entirely surrounding the turns or windings of the coil.

The portion 25 and end pieces 26 may be formed in a variety of ways. Forexample, they may be formed of sheet cellulose material treated with asolvent to dissolve or fuse adjacent portions thereof; or the cellulosematerial may be dissolved in a suitable solvent to form a varnish orpaint, which is sprayed, painted or in some other suitable mannerapplied to the core and spool heads of the coil. Another method is toapply cellulose material in strand form to the core and spool heads, andthen subject the associated strands to a solvent there for either beforeor after the electrical conductor is applled, in the manner describedabove for producing the exterior portion or the covering.

Where the process embodying the invention is employed for the purpose ofcovering coils wound on headed spools, it is essentialthat all of thewindings thereof. be covered and the coveringl material closely abut theends of the spool heads or the cellulose end pieces, as the case may be,in order to exclude moisture and the like from the windings of the coil.In order to prevent all shrinkage of the coverin and the possibility ofthe covering pulling away from the spool heads or the end pieces, thestrands may be given a simple treatment before they are applied to thecoil. This treatment consists in impregnating the strand with an agentwhich retards or prevents the hardening of the cellulose derivative uponthe evaporation of the solvent. An oil, a dye o'f coal tar derivation orsimilar substances may be used. Preferably castor oilis employed inwhich one part of castor oil is dissolved in about four parts of alcoholand the strands are then soaked vin this mixture until they arethoroughly impregnated. The strands are then removed from thealcohol-castor oil solution and thoroughly dried, after which they areapplied to form a covering in the manner described above.

The term cellulose material is used in the appended claims-to refereither to fibers or strands composed entirely or partially of syntheticfilaments or to natural fibers or strands impregnated with a cellulosederivative, and the term solvent as employed in the appended claims isintended to include plasticisers7 as well as true solvents.

What is claimed is:

1. A protective coatin for a body consisting of a film of a cell osederivative reinforced by bers of a cellulose derivative.

2. A protective coating for a body consisting of coalesced fibers of acellulose derivative.

3. A protective coating for a body consisting of coalesced unwovencellulose fibers.

4. A protective coating for a body consisting of a plurality of helicesof cellulose material surrounding the body, adjacent helices beingcoalesced.

5. A protective coating for an electrical coil consisting of a pluralityof coalesced fibers of a cellulose derivative surrounding the coiledconductor.

6. A protective coating for an electrical coil consist-ing of aplurality of coalesced helices of cellulose material surrounding thecoiled conductor.

7. A protective coating for an electrical coil consisting of a pluralityof coalesced helices of a cellulose derivative surrounding the coiledconductor.

8. A protective coating for an electrical coil consisting of animperforate envelope of coalesced cellulose material extending throughthe coil and entirely surrounding the coiled conductor. Y

9. A method of producing a protective coating, which consists inarranging in un- Woven Warp formation a plurality of lengths ofcellulose material in strand form, subjecting the assembled lengths to asolvent to dissolve portions thereof and thereby coalesce the adjacentlengths, and evaporating the solvent. A

10. A method of producing a lprotective coating, which consists inarranging cellulose material in strandform in a plurality of adjacenthelices, subjecting the helically arranged material to a solvent todissolve portions thereof and thereby coalesce the adjacent helices, andevaporating the solvent.

11. A method of roducing a protective coating for an electrical coil,which consists in positioning portions of cellulose material around andextending through the coil to completely surround the coiled conductor,subjecting the positioned material to a solvent to coalesce the adjacentportions of the material to form an imperforate coating completelyenveloping the coiled conductor,

and evaporating the solvent.

12. A method of producing a rotective coating for an electrical coil,Whic consists in applying a cellulose derivative in strand form aroundthe coil in a plurality of helices,

subjecting the applied strand to a solvent to dissolve portions thereofand thereby coalesce the adjacent helices, and evaporating the solvent.

13. A method of forming a protective coating, which consists in.impregnating cellulose derivative fibers with an agent for retardingthe hardening thereof, assembling the impregnated fibers, subjecting theassembled fibers to a solvent for the cellulose derivative to coalescethe adjacent libers, and evaporating the solvent.

14. An article of manufacture comprising a body and a covering ofcoalesced cellulose material therefor.

15. An article of manufacture comprising a body and an envelope thereforcomposed of coalesced fibers of a cellulose derivative.

16. An article of manufacture comprising an electrical coil and animperforate covering .therefor consisting of coalesced fibers ofcellulose material reinforced by untreated fibers.

In Witness whereof, I hereunto subscribe my name this 14th day of AugustA. D., 1925.

CLEM H. FRANKS.

